In a principal aspect the present invention relates to a pier construction for supporting structures in a soil matrix wherein the pier is formed with a special mechanical apparatus from an aggregate material by compacting successive lifts or sectors of the aggregate material located in a cavity in the matrix.
In U.S. Pat. No. 5,249,892, incorporated herewith by reference, a method and apparatus are disclosed for producing short aggregate piers in situ. The process includes forming a cavity in soil and then introducing successive layers of compacted aggregate material into the cavity to form a pier that can support a structure. The aggregate may be comprised of various materials. The lifts or layers of aggregate which are compacted during the pier forming process typically have a diameter of 1 to 3 feet and a vertical rise of similar dimension and range. Thus, such piers are made by drilling a hole or cavity in a soil matrix, placing aggregate or other select fill material in small discreet layers in the cavity, and then tamping each layer of the material in the cavity with a special mechanical tamper apparatus to provide impact or ramming energy to the layer of material. This apparatus and process produces a stiff and effective stabilizing element or pier. However, this method of pier construction has a limitation in terms of the depth to which the pier forming process can be accomplished economically. Typically the process described in the patent is limited to a depth of approximately 20 feet because of the equipment utilized, the time required to make a pier and the techniques that are available. Thus, there has developed a need for a mechanical apparatus, as well as a construction process, which can be successfully and economically utilized at greater depths yet have the attributes and benefits associated with the short aggregate pier method, apparatus and construction disclosed in U.S. Pat. No. 5,249,892.